1. Field of the Invention
This invention relates to medical instruments and in particular a system that establishes percutaneous access to a blood vessel or body cavity (which would include an abscess or pleural or peritoneal or pericardial or epidural or subarachnoid spaces).
2. Related Art
It is frequently necessary to establish access to an internal portion of the body for the purpose of removal of fluid, administration of medication, establishing a drainage path and the like. A typical application is placement of a catheter in a blood vessel for collection of blood over an extended period of time. This same catheter can be used for the intravenous administration of drugs and anesthesia. Delivery is not limited to vascular access but also for establishing caudal and lumber epidural blocks for the production of local or regional anesthesia by infiltration techniques. Another common use for catheter placement is to establish a drainage path for the pleural or peritoneal or pericardial spaces or from a surgery site or abscess.
As used herein, the term “proximal end” refers to that portion of the system that is above the skin line and is accessible. The term “distal end” refers to that portion of the system that is inserted into the body, such as the tip of the needle or end of the catheter.
A typical procedure involves the placement of a catheter, typically flexible and of a plastic material, into the space occupied area with the proximal end affixed at skin level. A thorocentesis kit may be used which employs a needle with a catheter mounted concentrically on the outside. The length of the needle is somewhat longer that the catheter so that the sharp tapered end projects beyond the end of the catheter. The outer end of the catheter is tapered to provide a smooth transition from the outer diameter of the needle to that of the catheter. The inner end of the catheter is sleeved with a connector for subsequent connection to a collection bag, syringe or cut-off valve. A syringe is attached to the end of the needle. The catheter is then free to slide on the outside of the needle but is prevented from coming off the needle at the proximal end by the attachment connector of the needle to the syringe.
In this procedure the needle pierces the skin and any underlying tissue carrying with it the catheter. Since the proximal end of the catheter is stopped by the syringe attachment, it advances at the same rate as the needle. Once a sufficient depth of penetration is achieved by the needle, the clinician simultaneously withdraws the needle while advancing the catheter. The needle acts as a guide for the catheter. Generally accumulation of a small amount of fluid in the syringe provides an indication that the needle has penetrated to the destination location. The catheter is advanced until its distal end is at the desired location and then the needle is totally withdrawn. The proximal end of catheter may then be attached to a collection bag for drainage or collection of bodily fluid. It may also be used as a port for the delivery of medicine by subsequent introduction of a needle with a syringe loaded with a drug. The catheter proximal end can also be fitted with a valve for capping the catheter.
One disadvantage of this technique is that the fact that the catheter-flow circuit must be broken in order to remove the introducer needle as the needle is removed the catheter is in open fluid communication with the environment so that air can enter into the cavity if the pressure gradient favors retrograde flow. Another disadvantage of this technique includes the possibility of an unintended needle stick of the clinician upon his or her withdrawal of the needle because of the technique and materials used in the above described system. Yet another disadvantage of this prior art technique is that the needle must be as long as the catheter making it cumbersome to handle and manipulate.
Another technique in use employs a large diameter needle that is used to establish access to the body location where the catheter will be placed. A wire is then passed inside the needle until it has reached the approximate location at or beyond the distal end of the needle. The needle is then withdrawn and the wire remains. A catheter is then slid over the wire as the wire is removed and the catheter remains behind. A problem with this technique involves the number of steps required each of which individually and collectively add levels of potential complications and/or inaccurate distal catheter placement. Frequently, the distal end of the catheter will abut or sometimes dig into the wall of the vessel preventing the withdrawal or delivery of fluid.